Data from drag strip

[Bob Valentine]

Another scenario could be a restricted exhaust would be interesting to put
some sort of pressure tap in the exhaust and see if it corrosponds with the
map drop.  I'd wittnessed the same MAP drop issue before I had a BBC
throttle body on the 403 Olds, but that was prob. an extreme case.   

I see IAT temps all over the place, my IAT is in the air cleaner on top of
the TB.   Gets warm during idle, easily cools off 10-30 degrees during
cruise.    Humidity is a factor also, more humid => more temp drop.   

-> Bob Valentine
-> bob at tecmark.com

At 10:41 PM 4/30/2001 -0700, you wrote:
>
>Good evening gents,
>
>I was @ the track the other day & was checking out the data tonight &
>thought I would run a few things by Y'all.
>
>we had a small discussion about Intake Air Temp a while back & I had noticed
>that by the time I was @ the end of the 1/4 that the IAT was about 3 degrees
>cooler (I have a super ram, cold air intake & a 383).  this I thought was
>pretty cool & had not noticed it before.  This time I went I was running
>slicks & I just noticed that even during the burn out (I was not doing a
>burn out with the radials, no sense, they went up in smoke any way), that
>the temp came down about 3/4 of a degree. I was doing about 45 to 55 second
>burn outs.  I had thought that it was flying down the track that was
>actually cooling the intake tract, thus reducing IAT's.  But it appears that
>just pulling air in does it.  just an observation is all.
>
>Second is that I noticed that the MAP was actually dropping as the motor
>came up to about 5200 rpm.  I take it to about 5700 to 6000 for the shift
>point & from 5200 to 5700 you can watch the MAP drop.  I could not figure
>out what was "wrong".  makes me think, one of two things.  first is that the
>383 has enough volume @ that RPM to start to draw a slight vacuum on the
>plenum (although I don't think so, that is why Lingenfelter made it so darn
>big) OR, that there might be a restriction upstream of the TB, that is
>allowing the motor to draw a vacuum on the plenum.  I think that the later
>is probably the case, cause of the Cold air tubes that I have.  I think that
>the next time to the track I am going to take my clothes dryer duct & some
>duct tape & do a couple of runs to experiment.  Also we had a discussion
>about IAT's & taking cold air from the engine bay (K&N right on TB vs. cold
>air package).  I forgot my TB K&N so I was not able to do that test.
>
>thoughts?
>
>Bob Wooten
>r71chevy at earthlink.net
>www.r71camaro.homestead.com
>
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